| 摘要 |
PURPOSE:To improve the response speed and the frequency characteristics, by varying the band gap of a material for a conductive channel region from the source toward the drain. CONSTITUTION:A conductive channel region 2 is formed of a material which sequentially changes the band gap. For example, AlxGa1-xAs is used as the material while the mixing ratio (x) of Al is changed from 0 in the drain to 0.5 in the source. According to such construction, when an electric field is applied from the source toward the source, the Fermi level EF is inclined and the conduction band EC is also inclined proportionally thereto. The inclination of the conduction band EC is provided by the summation of the inclination due to the electric field and the inclination due to the difference in Al mixing ratio (x). This means that the conduction band EC is inclined steeply even with a small electric field. The speed of carriers, which move from the source to the drain in such a steep inclination, is increased and hence the response speed of the element is also increased. |
